Conventionally, there is well known a rolling-element assembly used for rolling-contact bearings. An example of the rolling-element assemblies is disclosed in, for example Japanese Patent Laid-Open No. 2001-208084 in which more than one roller is held for rotation in a pocket in a cage and embedded in solid lubricant with a bearing circular surface thereof being exposed partially out of the solid lubricant. With the prior rolling-element assemblies of the sort recited earlier, however, the rollers are not combined with the cage into a unit and, therefore apt to come apart from the cage.
Moreover, Japanese Patent Laid-Open
No. 2000-145791 discloses a needle bearing or cam follower of maintenance-free type that is filled with sufficient amount of lubricant. The cam follower of maintenance-free type cited earlier leaves out a cage used commonly to hold more than one needle therein. Instead, there is interposed a separator made of polymer containing any lubricant therein. The separator is made with more than rectangular opening while a stud has no oil hole to supply lubricant through there. With the prior cam follower constructed as stated earlier, the separator, although made of polymer allowing the lubricant oozing over the rollers, needs the troublesome working of fitting many rollers into the rectangular openings, one to each opening, to complete the cam follower.
A bearing for cam follower is disclosed in, for example Japanese Utility Model Laid-Open No. 47417/1990, in which thrust washers are fit in an outer ring thick in axial cross-section where more than one roller is installed. With the cam follower with thrust washers recited just above, two pieces of thrust washer are installed for rotation on axially opposite ends of the outer ring in such a way that one is interposed between a circular surface of a flange on a stud end and an axially setback end in the outer ring while another is arranged between a circular surface of a retainer plate and another axially setback end of the outer ring, which is opposite axially to the first axial setback in the outer ring. The thrust washers are made of iron or steel member that is recessed partially on any one side thereof and coated with a skin. The prior cam follower, although assembled with thrust washers, has contained no solid lubricant therein.
Moreover, a mold for producing a tapered-roller bearing with lubricant-containing polymer is disclosed in, for example Japanese Patent Laid-Open No. 2001-330029, in which more than one tapered roller is confined between upper and lower mold halves and lubricant-containing polymer is poured into a mold cavity through an injection gate with the aid of interposing resilient member, thereby producing the tapered-roller bearing for low torque use, which is filled with lubricant-containing polymer. The prior production procedure recited above for the roller bearing has to go through several chores including getting the upper and lower mold halves mated precisely together with each other and also lubricant-containing polymer poured through the narrow or small injection gate into the mold.
Another process for producing a rolling bearing filled with lubricant-containing polymer is disclosed in, for example Japanese Patent Laid-Open No. 153144/1999, in which the lubricant-containing polymer is partially cut away at wedges flanking the line contact of the roller with the outer ring. This prior production process as stated just earlier also has to go through several chores including cutting away the lubricant-containing polymer at every wedge flanking the line contact of every roller with the outer ring, and also pouring the lubricant-containing polymer with the help of spacers.
A further another process for a rolling-contact bearing filled with solid lubricant is known as disclosed in, for example Japanese Patent Laid-Open No. 94893/1997, in which powdered thermoplastic resin mixed with lubricating grease is first poured into a clearance between an outer and inner ring of a rolling-contact bearing at ambient temperature, and then the rolling-contact bearing is fit in and clamped between upper and lower mold halves that has been previously heated. After the lubricant has hardened along surface area, which is in contact with the mold, into a lamellar structure, the rolling-contact bearing is transferred from the mold into a heating furnace where the rolling-contact bearing is heated, followed by cooled down to get the lubricant solidified entirely. The prior production method recited earlier, however, needs many manufacturing steps and several more chores including clamping overall the rolling-contact bearing between the mold halves.
Meanwhile, the stud-type roller bearing with tracking roller is generally used in a way fastened to any moving body with a stud made at a plain end thereof with male threads, which either extends through the moving body, followed by fitting into a female threaded hole in a nut or fits directly into a female threaded hole in the moving body. The tracking roller or the outer ring of the stud-type roller bearing comes into rolling contact with any counterpart to convert any motion of the counterpart to get the moving body making linear motion or curvilinear motion. The stud-type roller bearing with tracking roller constructed as stated earlier, although having been extensively employed for the cam-follower mechanisms or rolling-contact bearings for linear motion in printing machines, food processing machinery, liquid crystal display/semiconductor device manufacturing equipment, tool machines, industrial robots, office-automation machines, and so on, are needed recently to get further maintenance-free in construction, higher in hermetically sealed property and resistance against lopsided load and ready for long-life services, even with high performance.
With the stud-type roller bearing with tracking roller or the follower of rolling-contact bearing, one favorable scenario to deal with the demands as stated earlier is that the cage and more than one roller are all assembled together with solid lubricant into a complete unitary molding where three components: cage, more than one roller and solid lubricant are all integrated in such a way the lubricant fills a clearance between rolling element raceways to lubricate the rollers rolling between the raceways. Nevertheless, there still remains a major challenge to consider about how to make the complete unitary molding that is easy to handle the molding itself and simple to install the molding between any inside rotating member and an outer ring.